1. Field of the Invention
The present invention relates to a two-dimensional moving system for moving a table two dimensionally in a plane, such as X-Y table, in which a table is movable in an X (lateral) direction and a Y (longitudinal) direction, or a X-Z table in which a table is movable in the X direction and a Z (vertical) direction.
2. Related Art
FIG. 11 shows a known plane-type X-Y table, having a conventional structure, a two-dimensional moving system for moving a table in a plane (for example, as disclosed in Japanese Patent Publication No. SHO 63-9477). Such X-Y table comprises a table 1, a guide mechanism 2 for guiding the table to be movable in a plane, an X-axis driving mechanism 3 and a Y-axis driving mechanism 4.
Further, it is to be noted that the terms xe2x80x9cX-axis xe2x80x9cY-axis xe2x80x9d and xe2x80x9cZ-axis xe2x80x9d used herein may be substituted with terms xe2x80x9cX-directionalxe2x80x9d, xe2x80x9cY-directional xe2x80x9d and xe2x80x9cZ-directionalxe2x80x9d, in which X, Y and Z mean the axial directions (axes) normal to each other.
The guide mechanism 2 includes a base plate 5, columns (posts) 6, - - - , 6 disposed at four corner portions of the base plate 5, two X-axis slider shafts 7, 7 arranged in parallel between opposed two columns 6, 6, two Y-axis slider shafts 8, 8 arranged in parallel between other opposed two columns 6, 6, X-axis sliders 9, 9 mounted to the X-axis slider shafts 7, 7 to be slidable, Y-axis sliders 10, 10 mounted to the Y-axis sliders 8, 8 to be slidable, a Y-axis guide shaft 11 arranged between the X-axis sliders 9, 9, and an X-axis guide shaft 12 arranged between the Y-axis sliders 10, 10. Both the X-axis guide shaft 11 and Y-axis guide shaft 12 penetrate the table 1 so as to intersect to each other at right angles.
The X-axis driving mechanism 3 includes a Y-axis motor 13, a Y-axis driving shaft 14 connected to the Y-axis motor 13 and a pair of X-axis belt transmission devices 15, 15 fixed to the Y-axis driving shaft 14. Each of the X-axis belt transmission devices 15, 15 includes an X-axis belt 16, which is coupled to the X-axis slider 9 by means of bracket 17.
The Y-axis driving mechanism 4 includes an X-axis motor 19, an X-axis driving shaft 20 connected to the X-axis motor 19 and a pair of Y-axis belt transmission devices 21, 21 fixed to the X-axis driving shaft 14. Each of the Y-axis belt transmission devices 21, 21 includes an Y-axis belt 22, which is coupled to the Y-axis slider 10 by means of bracket 23.
Then, when the Y-axis motor 13 is driven to be rotated, the Y-axis driving shaft 14 is rotated, the X-axis belts 16, 16 are moved in the longitudinal direction thereof, and the X-axis sliders 9, 9 and the Y-axis guide shaft 11 are moved in the X-axis direction. According to such movement, the table 1 is moved in the X-axis direction. On the other hand, when the X-axis motor 19 is driven to be rotated, the X-axis driving shaft 20 is rotated, the Y-axis belts 22, 22 are moved in the longitudinal direction thereof, and the Y-axis sliders 10, 10 and the X-axis guide shaft 12 are moved in the Y-axis direction. According to such movement, the table 1 is moved in the Y-axis direction.
In the X-Y table of the structure mentioned above, the Y-axis guide shaft 11 is disposed between the X-axis belts 16, 16 extending in the X-axis direction, and when the Y-axis driving shaft 14 is driven to be rotated, the Y-axis guide shaft 11 is moved in the X-axis direction, and thereby, the table 1 is moved in the X-axis direction. On the other hand, the X-axis guide shaft 12 is disposed between the Y-axis belts 22, 22 extending in the Y-axis direction, and when the X-axis driving shaft 20 is driven to be rotated, the X-axis guide shaft 12 is moved in the Y-axis direction, and thereby, the table 1 is moved in the Y-axis direction.
However, in the conventional X-Y table of the structures mentioned above and shown, for example, in FIG. 11, there is a possibility that rotational angles of tandem pulleys 25, 25 of the belt transmission devices 15, 15 are changed at the driving time due to twisting (torsion) force of the Y-axis driving shaft 14, and the motion of one of the X-axis belts 16 disposed apart from the Y-axis motor 13 always delays from the motion of the other one of the X-axis belts 16 disposed near the Y-axis motor 13. Such delay of the motion also occurs on the Y-axis belts 22, 22. When the table 1 is moved at a highly accelerated speed, the twisting of the Y-axis driving shaft 14 and the X-axis driving shaft 20 is made large. Therefore, in the conventional X-Y table, it is impossible to move the table 1 at a highly accelerated speed.
In order to solve such problem, the Japanese Patent Publication mentioned hereinbefore provides an X-Y table having structure, as shown in FIG. 12, that the Y-axis driving shaft 14 or X-axis driving shaft 20 is driven at a central portion between the tandem pulleys 25, 25 so as to make equal the twisting amounts thereof and, hence, to substantially eliminate variation or change of the rotational angles of the tandem pulleys 25, 25. In such X-Y table, central driving devices 26, 26 are arranged at a central portion between the parallel paired X-axis belt transmission devices 15, 15 and a central portion between the parallel paired Y-axis belt transmission devices 21, 21, respectively.
However, in the X-Y table in which the rotational angle variation between the tandem pulleys 25, 25 are eliminated, the central driving devices 26, 26 merely serve to distribute a driving force to or between the tandem belt transmission assemblies (including a pair of X-axis belt transmission devices 15, 15 and a pair of Y-axis belt transmission devices 21, 21), and in an actual arrangement, the driving force is applied to the central position between the tandem belt transmission assemblies. That is, the driving force is focused and concentrated on the central portion in the longitudinal direction between the X- and Y-axis guide shafts 12 and 11. For this reason, when the table 1 is shifted from the central portion between the tandem belt transmission assemblies, it is impossible to position the driving force on the central portion of the table 1. Therefore, in the case where the table 1 is not accurately positioned on the central portion of the tandem belt transmission assemblies, there will cause a yawing (YAW) moment to the peripheral support bearings, which will be described hereunder in detail.
FIG. 13 shows a schematic arrangement of the X-Y table in which the rotational angle variation between the tandem pulleys 25, 25 is eliminated. With reference to FIG. 13, when the central driving device 26 drives the X-axis driving shaft 20, the tandem belt transmission assemblies 21, 21, and the X-axis guide shaft 12 is moved in the Y-axis direction. As shown in FIG. 13, the equally divided X-axis driving shaft 20 distributes a torque (T) equally to xc2xd torque (T/2) which equally balances a force of F/2 at both sides of the X-Y table. Finally, a composed force F is positioned on the central portion of the tandem belt transmission assemblies at both the sides of the X-Y table. When the table 1 is shifted from the central position by a distance D, since no means for controlling the supply of the torque exists on the closer side, the force F for acceleration is always applied to the central portion of the X-axis guide shaft 12. As a result, the yawing moment equal to Fxc3x97D is caused. In the case where such yawing moment is caused, it becomes difficult to move the table 1 at the highly accelerated speed.
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a two-dimensional moving system capable of moving a table or like at a highly accelerated speed without causing any moment such as yawing moment and achieving a high moving (motion) performance, that is, capable of effectively concentrating the accelerated speed on the table regardless of the position of the table when moved.
This and other objects can be achieved according to the present invention by providing a two-dimensional moving system for moving a table in a plane comprising:
a table;
a guide mechanism for guiding the table to be movable in the plane;
first and second belt members which are connected to the table so as to intersect to each other at substantially right angles;
a first driving mechanism for driving the first belt members so as to move the table in a longitudinal direction of the first belt members and to allow the first belt members to be movable in a longitudinal direction of the second belt members; and
a second driving mechanism for driving the second belt members so as to move the table in the longitudinal direction of the second belt members and to allow the second belt members to be movable in the longitudinal direction of the first belt members.
In the present invention, the first and second belt members each preferably comprises an annular endless member including, for example, timing belt, V-belt, chain or rope.
According to the present invention of the structure mentioned above, since the table is moved by driving the first and second belt members, the accelerated force can be effectively concentrated to the table regardless of the position of the table. Further, the moving load including the weight of the table and the load applied thereto is larger than a moving load preliminarily applied to a movable portion of the guide mechanism. However, according to the structure of the present invention, since any yawing moment is not caused, the table can be moved at a high acceleration speed, thus achieving the improved moving performance.
In a preferred embodiment of the present invention, the first driving mechanism comprises a pair of first pulleys provided for both end portions of the first belt members, a first spline shaft extending in parallel to the longitudinal direction of the second belt members so as to penetrate one of the first pulleys and a first driving source for driving the first spline shaft to be rotated, this one of the first pulleys being movable in an axial direction of the first spline shaft and being rotated thereby, and the second driving mechanism comprises a pair of second pulleys provided for both end portions of the second belt members, a second spline shaft extending in parallel to the longitudinal direction of the first belt members so as to penetrate one of the second pulleys and a second driving source for driving the second spline shaft to be rotated, this one of the second pulleys being movable in an axial direction of the second spline shaft and being rotated thereby.
According to this embodiment, the first belt member is rotated and the first belt member can be moved in the longitudinal direction of the second belt member. Furthermore, the second belt member is rotated and the second belt member can be moved in the longitudinal direction of the first belt member. The use of the spline shaft makes simple the structures of the first and second driving mechanisms, improving the reliability. Moreover, even if the driving sources are disposed at corner portions of the X-Y table for the sake of easy usage, the acceleration force can be concentrated to substantially the central portion of the table without using, for example, wrapping transmission member.
The pulleys may be timing pulleys and the belt members may be timing belts.
According to the use of the timing belt having less slip or noise, the table can be smoothly moved at a high acceleration speed and backlash is eliminated, thus improving the positioning performance.
In a further embodiment, the guide mechanism comprises a pair of first guide shafts extending in parallel to the longitudinal direction of the first belt members so as to guide the table to be movable, a pair of second guide shafts extending in parallel to the longitudinal direction of the second belt members so as to guide the table to be movable, a pair of first linear motion guides provided for both end portions of the first guide shafts and adapted to guide the linear motion of the first guide shafts in the longitudinal direction of the second belt members, and a pair of second linear motion guides provided for both end portions of the second guide shafts and adapted to guide the linear motion of the second guide shafts in the longitudinal direction of the first belt members, a pair of the first guide shafts being arranged on both sides of the first belt members and a pair of the second guide shafts being arranged on both sides of the second belt members.
According to this embodiment, since the paired first guide shafts are arranged on both sides of the first belt members and the paired second guide shafts are arranged on both sides of the second belt member, the table can be smoothly guided in a balanced state even if the table is moved at the highly accelerated speed.
In a further embodiment, each of the first pulleys is guided by each of the first linear motion guides so as to be linearly moved in the longitudinal direction of the second belt member and each of the second pulleys is guided by each of the second linear motion guides so as to be linearly moved in the longitudinal direction of the first belt members.
According to this embodiment, the motion of the table can accord with the motions of the first and second belt members, and hence, the table can be moved at the highly accelerated speed.
In a further embodiment, the first and second spline shafts are formed with ball rolling grooves extending in axial directions thereof, the above-mentioned one of the first pulleys and the above-mentioned one of the second pulleys are formed with ball circulation passages including ball rolling grooves corresponding respectively to the ball rolling grooves formed to the first and second spline shafts, and an outer sleeve is assembled to each of the first and second spline shafts to be linearly movable thereto and a number of balls housed and arranged in the ball circulation passage of the outer sleeve so as to circulate in accordance with the linear motion of the outer sleeve with respect to each of the first and second spline shafts.
According to this embodiment, the pulleys can be smoothly moved in the axial direction of the spline shafts through the rolling motion guide, and as a result, the table can be moved at the highly accelerated speed.
In a further embodiment, the linear motion guides each comprises a track shaft having a rolling member rolling surface, a slider member formed with a rolling member circulation passage including a loaded rolling member rolling surface corresponding to the rolling member rolling surface of the track shaft and assembled with the track shaft to be relatively movable, and a number of rolling members arranged in the rolling member circulation passage so as to circulate therein in accordance with the relative motion of the slider member with respect to the track shaft.
According to this embodiment, the motion of the linear motion guide device can be made smooth through the rolling motion of the rolling members, and hence, the guide shafts and the table can be moved at the highly accelerated speed.
In a further embodiment, the first and second belt members are coupled to substantially a central portion of the table in the plane.
According to such structure, the accelerated force can be more effectively concentrated to the central portion of the table, so that the table can be moved at the more highly accelerated speed.
In a further embodiment, the table comprises an upper table section and a lower table section which are shifted from each other in positions in a direction normal to the plane, and one of the first and second belt members is coupled to the upper table section and the other one thereof is coupled to the lower table section.
According to this embodiment, the belt attaching positions are shifted in the vertical direction, so that the interference between the first and second belt members can be prevented even if they intersect to each other.